Durability performance of concrete incorporating spent fluid cracking catalyst R. Neves a,⇑ , C. Vicente a , A. Castela a,b , M.F. Montemor b a Barreiro Technology School, Polytechnic Institute of Setúbal, R. Américo da Silva Marinho, 2939-001 Barreiro, Portugal b ICEMS, Instituto Superior Técnico, ULisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal article info Article history: Received 21 April 2014 Received in revised form 11 September 2014 Accepted 28 September 2014 Available online 8 October 2014 Keywords: Concrete Zeolites Corrosion inhibitor Permeability Carbonation resistance Chloride resistance abstract The petrochemical industry uses, in its fluid catalytic cracking units, zeolites as catalysts. After several cycles of use and regeneration, the fluid cracking catalyst becomes spent (SFCC). Given its chemical com- position (aluminosilicates), SFCC may be used as admixtures in mortar and concrete production. The aim of this study was to investigate the influence of SFCC in durability related properties of concrete, namely in air permeability, capillary suction, carbonation and chloride resistance, considering also its simulta- neous use with corrosion inhibitors. An experimental program was developed comprising four concrete mixes, sampled in two batches. The water-binder (cement + SFCC) ratio and the plasticizer dosage were kept constant. Statistical analyses of results were performed. Although no synergic effect of the combined use of SFCC and corrosion inhibitor was found, SFCC revealed to be an interesting supplementary cement- ing material for concrete regarding its durability and the associated positive environmental impacts. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction The petrochemical industry uses, in its fluid catalytic cracking units, zeolites as catalysts. The zeolites promote breaking and rear- rangement of the hydrocarbon molecules in order to generate new products. After several cycles of use and regeneration, the fluid cracking catalyst becomes spent, due to the accumulation of heavy metals and carbon, from the hydrocarbon stream, on their surface. These spent fluid cracking catalysts (SFCC), given its chemical com- position (aluminosilicates) may be used as admixtures in concrete. The incorporation of SFCC in concrete production brings envi- ronmental and economic benefits. Besides being a reutilization of a waste product, it can be used to partially replace cement, thus decreasing concrete final cost and the environmental impacts related to cement production. According to Marafi and Stanislaus [1] indicators, the estimated total quantity of SFCC generated worldwide in 2013 is around 180,000 tons. This amount of SFCC can be easily used by incorporating in concrete, as the 2012 world cement production was 3700 million tons [2]. Actually, a selective use of SFCC in concrete production is foreseen. References about SFCC pozzolanic activity can be found in literature [3–9], as well as about its contribution for the acceleration of the hydration and setting processes [4] and for increasing the compressive and flexural strength [9–11]. Nowadays, performance assessment of a concrete mix is not limited only to workability and compressive strength testing. Due to the growing relevance of life cycle cost analysis, the durabil- ity issues are of primordial importance within the aim of evaluat- ing the suitability of a concrete mix or constituent. Most of the concrete deterioration mechanisms require the ingress of aggres- sive agents from the environment. Thus, concrete transport prop- erties, are one of the governing factors in concrete durability. Afterwards, chemical reactions between aggressive agents and concrete constituents also play an important role. This is also valid for reinforced concrete, where steel corrosion is the deterioration mechanism most commonly found. Prior to corrosion onset, usu- ally, there is either concrete carbonation or the presence of chlo- ride ions, or both [12]. One approach to prevent reinforced concrete deterioration due to steel corrosion is through the use of corrosion inhibitors [13–17] that in general are added to the concrete mixture or applied on the concrete surface. Organic compounds like mixtures of alkanolam- ines (AMAs), amines or amino-acids are used as corrosion inhibi- tors. However, there is some controversy regarding their use. Elsener et al. [18] reported that they are not effective against chlo- ride induced corrosion, whereas Bavarian and Reiner [19] found that AMAs are protective. Jamil et al. [15,16,20] observed that these inhibitors are effective as they can prevent corrosion, due to the formation of a protective surface film, and even repair active areas. Most of the problems related with low effectiveness have been associated with leaching and evaporation of AMAs volatile http://dx.doi.org/10.1016/j.cemconcomp.2014.09.018 0958-9465/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +351 212 064 660; fax: +351 212 075 002. E-mail address: rui.neves@estbarreiro.ips.pt (R. Neves). Cement & Concrete Composites 55 (2015) 308–314 Contents lists available at ScienceDirect Cement & Concrete Composites journal homepage: www.elsevier.com/locate/cemconcomp